PROJECT SUMMARY Candidate: Dr. Jaitovich academic training, research experience and intense drive place him in an excellent position for a successful career as an independent physician/scientist. Dr. Jaitovich is an Argentinean immigrant who has developed extensive expertise in the field of protein turnover and degradation, and has worked in collaboration with Nobel Prize- winner Aaron Ciechanover, which reflects his remarkable standard of training in that field. In addition, he has been recruited as Assistant Professor of Pulmonary and Critical Care Medicine at Albany Medical College based on feedback he received upon submission of his NRSA award. At that time, and due to his strong interest in skeletal muscle atrophy in the context of pulmonary diseases, he was recommended to find an institution with higher expertise in muscle biology. He has recently established collaborations with two world experts in animal models of emphysema: Drs. Jack Elias and Jeanine D?Armiento, who will provide him the opportunity to test his hypotheses in complementary transgenic animals with previously developed lung disease. Dr. Jaitovich intends to pursue a career in academic medicine with a strong commitment to innovative basic and translational research. He has used his fellowship training to gain expertise in cell biology and in murine models of disease. Supported by this award, he will establish a novel niche within the area of muscle atrophy in the context of advanced pulmonary disease. Training supported by this K01 award will allow him to pursue his career as an independent investigator. Environment Mentorship: The Division of Pulmonary and Critical Care Medicine and the Center for Cardiovascular Sciences at the Albany Medical College are committed to fostering the academic careers of outstanding junior faculty like Dr. Jaitovich. Drs. Harold Singer, Yong-Xiao Wang and Dale Tang are well-funded, established investigators with a long track record of training. Their laboratories have the tools and resources required to complete the proposed studies, which have been specifically crafted to develop a novel and innovative research program independent from their own, and which will facilitate Dr. Jaitovich career. In addition, Dr. Jaitovich will receive full collaboration from Dr. Jacob Sznajder (Northwestern University), who is an expert in CO2-mediated cell signaling; Dr. Jack Elias (Brown University), who is an expert in animal models of emphysema/COPD; Dr. Jeanine D?Armiento (Columbia University), who is also an expert in animal models of emphysema and has described one of the first transgenic animals of that kind (lung MMP1+/- expression); Dr. Gustavo Nader (Penn State University), who has advanced expertise in regulation of anabolism in skeletal muscle; Dr. Esther Barreiro (Universitat Pompeu Fabra, Barcelona), a leading scientist in the field of COPD- associated muscle atrophy; and Dr. Jiang Qian (Albany Medical Center), who is the head of the neuromuscular core at the Department of Pathology of AMC. Environment: Dr. Jaitovich will conduct his research training in the Division of Pulmonary and Critical Care Medicine and the Center for Cardiovascular Sciences at the Albany Medical College (AMC). Additionally, he will have off-site collaboration from Northwestern University, Brown University, Columbia University, Penn State University, and Universitat Pompeu Fabra (Spain). Strong collaborations between the different federally funded investigators in this institution combined with their interactions with investigators in the AMC community and around the world provide an ideal environment for Dr. Jaitovich to develop an independent research program. Research: High CO2 in the blood or hypercapnia is common in patients with chronic obstructive pulmonary disease (COPD). These patients frequently develop skeletal muscle atrophy. Both hypercapnia and skeletal muscle atrophy are independent predictors of worse outcome in these populations. We recently reported that exposure to high CO2 leads to muscle atrophy and anabolic suppression in vitro and in vivo. This process occurs via CO2-induced AMPK phosphorylation, which targets the transcription factor FoxO3a, which (after nuclear translocation) induces the expression of the muscle-specific E-3 ligase MuRF1. These events lead to proteasome-mediated protein degradation and muscle atrophy. Here, we plan to expand our mechanistic insight and determine how hypercapnia causally leads to AMPK activation and net muscle loss; and evaluate these processes in skeletal muscles from emphysematous mice. Specific Aim 1: To determine the mechanism leading to AMPK phosphorylation under CO2 stimulation. We will explore the upstream signals that mediate high CO2-induced AMPK phosphorylation with particular emphasis to the distinct influence of calcium currents and mitochondrial dysfunction. To do that, we will use gain and loss-of-function approaches to determine the effect of CO2 on muscle cell signaling. Specific Aim 2: To determine whether hypercapnia leads to an AMPK-dependent down-regulation of skeletal muscle anabolism through phosphorylation of TIF-1A. We will investigate if high CO2-induced down regulation of 45s pre-rRNA occurs through the AMPK?1-mediated phosphorylation of TIF-1A and decreased TIF-1A/TBP- SL1 interaction, precluding the assembly of functional transcription initiation complexes. Specific Aim 3: To determine if genetically modified animals that develop pulmonary emphysema (IL-13 and MMP1+/-) display accelerated skeletal muscle atrophy under high CO2 compared to wild type littermates. We will also explore the relevance of the AMPK-MuRF1 axis in that process; and the rate of muscle anabolism in normo and hypercapnia in both wild type and transgenic mice.